Here is a little history:The first commercially successful vibrato arm was the Bigsby vibrato tailpiece, most often just called a Bigsby, and invented by Paul Bigsby (US Patent D169120 filed in 1952, issued in 1953).[10] The exact date of its first availability is uncertain, as Bigsby kept few records, but it was on Bigsby-built guitars photographed in 1952, in what became its standard form. In several interviews, the late Merle Travis, for whom Bigsby designed his first vibrato, recalled the prototype as being built for him in the "late '40s". The design uses a spring-loaded arm that rotates a cylindrical bar in the tailpiece, varying the string tension to create vibrato and other pitch variations. The string tension is balanced against a single, short helical compression spring, positioned under the arm pivot. The spring on the original tailpiece for Merle Travis was a Harley Davidson valve spring, as this was the only one Bigsby could find that would return to tolerance (and pitch). When a young cash-strapped John Lennon lost the spring in his Bigsby, he got a flesh-colored replacement from someone who worked on artificial limbs. Pioneering blues-rock guitarist Lonnie Mack was known for using a Bigsby on his famous 1958 Gibson Flying V. The term whammy bar is believed to derive from Mack's 1963 instrumental hit, "Wham!", in which Mack made liberal use of the Bigsby.To this day, the Bigsby enjoys some popularity, especially on hollow-body guitars, and is available as a factory-fitted option on top-line models both hollow- and solid-bodied from many makers, and as an aftermarket addition (requiring some skill to fit however). It remains the only widely used design whose mechanism is entirely above the belly of the guitar body, making it the only design particularly suitable for acoustic and semi-acoustic guitars.